The present invention relates to an air-suspension system for a vehicle, especially a closed or partly closed system.
An air-suspension system of the general type under consideration is described in DE 199 59 556 C1.
In such conventional air-suspension systems there is provided at least one air-suspension bellows which, via a valve arrangement, can be placed in communication with at least one further component of the air-suspension system in order to selectively increase or decrease the compressed-air quantity contained therein. In the known air-suspension system described in DE 199 59 556 C1, a compressed-air delivery device such as a compressor is used as such a further component, which serves, on the one hand, to pump air as needed from a compressed-air accumulator into the air-suspension bellows, and, on the other hand, to pump air as needed from the air-suspension bellows back into the compressed-air accumulator. To establish the necessary compressed-air communications, the valve arrangement is provided, which permits changeover between the two compressed-air delivery directions.
In this process, it may occur that—if an increase of the compressed-air quantity in the air-suspension bellows is to be achieved—the air pressure in those further components of the air-suspension system with which the air-suspension bellows is in communication via the valve arrangement is lower than in the air-suspension bellows. In this situation, an undesired decrease of the compressed-air quantity in the air-suspension bellows takes place at first, until pressure equality is established. In the case where a decrease of the compressed-air quantity in the air-suspension bellows is to be achieved, a higher air pressure may be present in a further component of the air-suspension system than in the air-suspension bellows. This leads, at first, to an undesired increase of the compressed-air quantity in the air-suspension bellows. Depending on the size of the volumes present in further components of the air-suspension system, such behavior may prove to be disruptive for the function of the air-suspension system, since changes in the compressed-air quantity in the air-suspension bellows lead to changes in the level height of the vehicle body.